/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.lucene.search.similarities;
/**
* F1LOG is defined as Sum(tf(term_doc_freq)*ln(docLen)*IDF(term))
* where IDF(t) = ln((N+1)/df(t)) N=total num of docs, df=doc freq
*
* @lucene.experimental
*/
public class AxiomaticF1LOG extends Axiomatic {
/**
* Constructor setting s only, letting k and queryLen to default
*
* @param s hyperparam for the growth function
*/
public AxiomaticF1LOG(float s) {
super(s);
}
/**
* Default constructor
*/
public AxiomaticF1LOG() {
super();
}
@Override
public String toString() {
return "F1LOG";
}
/**
* compute the term frequency component
*/
@Override
protected float tf(BasicStats stats, float freq, float docLen) {
if (freq <= 0.0) return 0f;
return (float) (1 + Math.log(1 + Math.log(freq)));
}
/**
* compute the document length component
*/
@Override
protected float ln(BasicStats stats, float freq, float docLen) {
return (stats.getAvgFieldLength() + this.s) / (stats.getAvgFieldLength() + docLen * this.s);
}
/**
* compute the mixed term frequency and document length component
*/
@Override
protected float tfln(BasicStats stats, float freq, float docLen) {
return 1f;
}
/**
* compute the inverted document frequency component
*/
@Override
protected float idf(BasicStats stats, float freq, float docLen) {
return (float) Math.log((stats.getNumberOfDocuments() + 1.0) / stats.getDocFreq());
}
/**
* compute the gamma component
*/
@Override
protected float gamma(BasicStats stats, float freq, float docLen) {
return 0f;
}
}